JPH0510271B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) (Problems to be Solved by the Invention) The present invention controls the electric motor of a steering force booster that generates auxiliary torque in accordance with the traveling speed of the vehicle. The present invention relates to an electric power steering device.

(Prior art) In general, in manual steering devices, the steering torque is small when driving at high speeds and becomes large when driving at low speeds, so in electric power steering devices, the auxiliary torque applied by the electric motor is large when driving at low speeds and small when driving at high speeds. do,
It is desirable that it be approximately equal to the manual steering device.

In this type of electric power steering device,
Equipped with a steering force booster powered by an electric motor and its analog control circuit, the system detects the steering torque applied to the steering wheel and the vehicle speed, and reduces the armature voltage of the electric motor in response to an increase in vehicle speed. , feedback control is performed based on the armature current of the motor, and the drive of the motor is stopped at a predetermined high speed or higher.

(Problems to be Solved by the Invention) However, when controlling the electric motor as described above using a microcomputer, due to the characteristics of the microcomputer, it is not possible to read many inputs at the same time, and the microcomputer has internal Since the control operates based on the clock pulses that the control unit has, it takes a certain amount of time for signal processing, so it takes a long time to complete the control, especially with conventional feedback control that repeats the feedback loop many times. response may deteriorate. Therefore, it has been difficult to adequately follow various changes in the steering device, and to appropriately improve the steering feeling.

Furthermore, since the drive of the electric motor is stopped above a predetermined high speed, when driving at such high speeds, the friction of the steering force booster, that is, the friction of the electric motor, reduction gear, and other sliding parts, causes the general It was heavier than a manual steering device, and the beginning of steering felt heavy and had a feeling of friction, which could reduce the steering feeling.

(Purpose of the Invention) Therefore, the present invention uses a microcomputer to determine a control signal for the electric motor based on a steering torque detection signal and a vehicle speed detection signal, without performing feedback control as in the past. This electric motor improves the responsiveness of the electric motor to provide an optimal steering feel, and eliminates the weight of the steering device caused by the friction of the steering force booster, providing a smooth steering feel when driving at high speeds. The purpose of the present invention is to provide a power steering device.

(Means for solving problems and their effects) FIG. 1 is an overall configuration diagram of the present invention.

In FIG. 1, when the ignition key switch is turned on, the steering torque detecting means 3
1. Various detection signals are output from the vehicle speed detection means 40. When the steering wheel is steered, based on the steering torque detection signal from the steering torque detection means 31, the road load control signal determination means 30B of the motor control signal generation means 30A determines and outputs a control signal corresponding to the road load. At the same time,
The friction control signal determining means 30C determines and outputs a control signal corresponding to the friction, and the vehicle speed coefficient determining means 30D decreases as the vehicle speed increases based on the vehicle speed detecting means from the vehicle speed detecting means 40 to reach a predetermined high speed. In the above, a vehicle speed coefficient that is zero is determined. Furthermore, the control signal corresponding to the road surface load is multiplied by the vehicle speed coefficient in the arithmetic circuit 30E, and the control signal corresponding to the friction is added to this output signal in the arithmetic circuit 30F. The motor control signal generating means 30A outputs a motor control signal to the motor driving means 45 based on the output signal from the arithmetic circuit 30F. Therefore, while the torque generated by the electric motor decreases as the vehicle speed increases, a torque equivalent to the friction of the steering force booster system is generated.Especially in high-speed driving ranges, the torque generated by the electric motor decreases as the vehicle speed increases. Not only can a steering feeling equivalent to that of a steering device be obtained, but also a smooth steering feeling can be obtained even at a predetermined high speed or higher.

(Embodiment) A preferred embodiment of the present invention will be described below based on the accompanying drawings.

FIG. 2 is a vertical view showing the electromagnetic booster 1 of this embodiment bent at 90 degrees. In FIG. 2, 1 is an electric power steering device, 2 is a steering column, 3 is a stator, and 4 and 5 are an input shaft and an output shaft coaxially arranged with each other. Further, as shown in FIG. 2, the inner end of the input shaft 4 is rotatably supported within the inner end of the output shaft 5 via a bearing 6, while these inner ends are connected by a torsion bar 12. Input shaft 4 has bearings 6 and 7
As a result, the output shaft 5 is rotatably supported by bearings 8 and 9, respectively. Further, a steering rotation sensor 16 is provided around the input shaft 4, a steering torque sensor 17 is provided around the fitting portion of the input/output shafts 4 and 5, and an electric motor 18 is provided around the output shaft 5. It includes a control device that drives and controls the electric motor 18 based on detection signals from a deceleration mechanism 18, a steering rotation sensor 16, and a steering torque sensor 17.

To explain in more detail, the steering rotation sensor 16 is
It is composed of a DC generator 16a fixed to the outer periphery of the column 2. In particular, the generator 16a has its rotating shaft disposed along the axis of the input shaft 4, and the input shaft 4 corresponds to the pulley 16b attached to the end of the shaft.
A belt groove 4a is formed on the outer periphery of the belt. A belt 16c is stretched between the belt groove 4a and the pulley 16b, and as the input shaft 4 rotates, the generator 16a rotates, and a detection signal corresponding to the rotation direction and rotation speed of the input shaft 4 is output. be done.

The steering torque sensor 17 is composed of a cylindrical movable iron core 17a provided on the outer periphery of the fitting portion of the input shaft 4 and the output shaft 5 so as to be displaceable in the axial direction, and a coil portion 17b fixed to the inner periphery of the steering column. It consists of a differential transformer. The movable iron core 17a is
Pins 17e projecting from each projecting piece of the output shaft 5, and elongated holes 17g that engage with pins 17f projecting from the input shaft 4, shifted by 90 degrees with respect to these pins 17e.
and 17h. The elongated hole 17h is inclined at a required angle with respect to the axial direction, and the elongated hole 17g is formed along the axial direction. Therefore, when an angular difference occurs between the input shaft 4 and the output shaft 5, the movable core 17a moves in the axial direction, and the movable core 17a is displaced in response to the steering torque applied to the input shaft 4. do. The coil portions 17b disposed around the movable core 17a include a primary coil 17k into which alternating current signals such as pulses are input, and a coil portion 17b which outputs an output signal corresponding to the displacement of the movable core 17a and is disposed on both sides of the primary coil 17k. A pair of secondary coils 171, 17m installed
It consists of Therefore, the angular difference between the input shaft 4 and the output shaft 5 due to the twisting of the torsion bar 12 results in an axial displacement of the movable iron core 17a, and the secondary coil 17
1.17m, it is converted into an electrical signal and output.

The electric motor 18 includes a stator 3 that is integrally provided with the steering column 2, and a stator 3 that is integrally provided with the steering column 2.
at least one pair of magnets 3a fixed to the inner peripheral surface of
, a rotor 18c rotatably disposed around the output shaft 5, and a brush 18d radially pressed by a spring within a brush holder fixed to the stator 3. The rotor 18c is the bearing 1
The cylinder shaft 18e is rotatably supported by 0 and 11.
A laminated iron core 18f having a skew groove and a multiple winding 18g are sequentially and integrally encased around the outer periphery of the cylindrical shaft 18e, and a minute gap is provided between the outer periphery of the magnet 3a and the iron core 18f. . Also, cylinder shaft 1
8e has a commutator 18h connected to multiple winding 18g.
The brush 18d is pressed against the brush 18d.

The speed reduction mechanism 19 includes a cylindrical shaft 18e of the electric motor 18.
A sun gear 19a formed on the outer periphery of the other end, and a ring gear 19b formed on the inner periphery of the stator 3.
and three planetary gears 19c interposed between these sun gear 19a and ring gear 19b.
and a carrier member 19d that pivotally supports the planetary gear 19c and is integrally connected to the output shaft 5, and the rotation of the rotor 18c of the electric motor 18 is transmitted to the output shaft 5 while being decelerated.

Next, the above control device will be explained based on FIG. 3.

In FIG. 3, 30 is a microcomputer, and the microcomputer 30 receives detection signals S ₁ to S ₄ from the steering torque detection means 31, the steering rotation detection means 35, and the vehicle speed detection means 40.
_S5 is inputted via the D converter 38 and via the I/O board within the microcomputer 30, respectively, based on instructions from the microcomputer 30.

The steering torque detection means 31 appropriately divides the clock pulse _T1 inside the microcomputer 30 to the steering torque sensor 17 and the primary coil 17k of this steering torque sensor 17, and converts it into a rectangular wave or a sine wave alternating current. a drive unit 32 that amplifies the current, a rectifier circuit 33A, 33B that rectifies each electrical signal obtained from the secondary coils 171 and 17m in response to the displacement of the movable core 17a, and a stable direct current that removes high frequency components. It is composed of low-pass filters 34A and 34B that convert into voltage.

The steering rotation detection means 35 includes the steering rotation sensor 16
It is composed of a DC generator 16a, subtraction circuits 36A and 36B that subtract the output of the DC generator 16a to detect its direction and magnitude, and low-pass filters 37A and 37B that remove high frequency components.

The vehicle speed detection means 40 includes, for example, a vehicle speed sensor 41 consisting of a magnet 41a that rotates together with a speedometer cable and a reed switch 41b that is turned on and off as the magnet rotates;
a pulse conversion circuit 42 that supplies power to the reed switch 41b and outputs the disconnection of the reed switch 41b as a pulse signal;
and a waveform shaping circuit 43 that shapes and outputs the output signal.

The microcomputer 30 is an I/O boat,
It is composed of a memory, an arithmetic section, a control section, a clock generator, etc., and operates based on clock pulses from a crystal oscillation circuit 38. Therefore, when the key switch is turned on, the microcomputer 30
Based on the command, each detection signal _S1 to _S4 is digitally converted by the A/D converter 38, and _S5 is processed according to the program written in the memory, and control signals _T2 and T that drive the electric motor 18 are generated. ₃ and T ₄ are outputted to the motor drive means 45 to drive and control the motor 18.

The motor drive means 45 includes a drive unit 46
and FET (field effect transistor) 47, 48, 4
It is composed of a bridge circuit consisting of 9,50 circuits. In the bridge circuit, the respective drain terminals of FETs 47 and 50 are connected to the A terminal of the power supply circuit, while their source terminals are connected to the other FETs 48 and 4.
They are connected to the drain terminals of 9, respectively. FET
The source terminals 48 and 49 are connected to the common side and connected to one terminal of the battery. FET47,
The gate terminals of 48, 49, and 50 are connected to the output side of the drive unit 46, and the source terminal of FET 47 and FET 5, which are the output side of the bridge circuit, are connected to the output side of the drive unit 46.
0 source terminal is the armature winding 1 of the motor 18
Connected to 8g. The drive unit 4
6 operates the FET 47 based on the motor rotation direction control signals T ₂ and T ₃ from the microcomputer 30.
At the same time as the ON drive, the FET 49 is enabled to drive, and the FET 49 is driven based on the motor drive signal T ₄ consisting of a PWM signal, or the FET 49 is driven.
At the same time as turning ON the FET 48, the FET 48 is enabled to be driven, and the FET 48 is driven based on the motor drive signal _T4 consisting of a PWM signal. Therefore, in the motor drive means 45, one FET 47
ON drive and FET49 PWM drive, or the other
Due to the ON drive of the FET 50 and the PWM drive of the FET 48, the rotation direction and power (rotation speed and torque) of the electric motor 18 are controlled according to the control signals T ₂ , T ₃ and T ₄ .

Next, the action will be explained.

FIG. 4 is a flowchart showing an outline of the motor control processing in the microcomputer 30, and P ₁ to _{P 33} in the figure indicate each step of the flowchart.

When the key switch of the ignition key is turned ON, power is supplied to the microcomputer 30 and other circuits, and control is started. First, in the microcomputer 30, data in each register and RAM are cleared. and,
In steps P ₁ and P ₂ , the steering torque detection signal
Read S ₁ and S ₂ sequentially. Here, since the steering torque sensor 17 is constituted by a differential transformer, the relationship between the steering torque and the detection signals S ₁ and S ₂ is shown as shown in FIG. Loaded steering torque detection signal
If S ₁ and S ₂ are normal, proceed to step P ₃ . In step _P3 , S ₁ -S ₂ is calculated, and this is set as the steering torque T, which is shown as shown in FIG.

In step _P4 , in order to determine the direction of action of the steering torque T, it is determined whether it is positive or negative. If it is positive, step _P5 sets F=0.
Proceed to step P ₈ , if negative, proceed to step P ₆ F = 1
After that, in step _P7 , absolute value conversion is performed, that is, T=
- Process T and proceed to step _P8 . here,
F indicates the sign of the steering torque T, that is, the direction of action. At step _P8 , the contents of the memory whose address is the absolute value T of the steering torque are shown in Table 1.
is called from. Table 1 shows the product of the electric current I _M of the motor 18 corresponding to the absolute value T of the steering torque shown in FIG. 6 and the resistance R _M of the armature winding, brushes, wiring, etc., that is, R _M A friction control signal DF(T), which is a duty conversion value obtained by I _M , is stored. At step _P9 , the contents of the memory whose address is the absolute value T of the steering torque are read from the table 2. Table 2 is shown as shown in FIG. 7, and stores the road load control signal D _L (T), which is a duty conversion value obtained from R _M ·I _M.

Next, in step _P10 , the vehicle speed detection means 40
Read the vehicle speed detection signal _S5 from this vehicle speed detection signal
Measure the period tv of the vehicle speed v based on _S5 and step
Proceed to P ₁₂ . At step _P12 , the contents of the memory whose address is period tv are read from table 3. Table 3 stores a vehicle speed coefficient K(t) determined by addressing vehicle speed v and period tv as shown in FIGS. 8 and 9, and this vehicle speed coefficient K(t) is decreases as the vehicle speed v increases,
It is set to be zero above a predetermined high speed v _HO . In step _P13 , the road surface resistance control signal D _L (T) is multiplied by the vehicle speed coefficient K(t), and this is set as D' _L (T), and the process proceeds to step _P14 . Therefore, D′ _L (T) becomes smaller as the speed increases, and becomes zero at a predetermined high speed v _HO or higher. In step P ₁₄ , the friction control signal D _F (T) is added to D′ _L (T), and this is used as the motor torque control signal D ₁
Proceed to step _P15 . Therefore, the motor torque control signal D ₁ corresponds to the magnitude of the vehicle speed v as shown in FIG. 10, and at a predetermined high speed v _HO or higher, the value of the control signal corresponds to the friction. Note that v ₀ indicates when the vehicle is stopped, v _L indicates a low speed, v _H indicates a high speed, and v _HO indicates a predetermined high speed or higher. Further, in step _P15 , the value of F is determined in order to give a sign to the motor torque control signal _D1 .
If F=0, _D1 is positive, so the process goes directly to step _P17 . If F=0, _D1 is negative, so _D1 = _-D1 is set in step _P16 , and then the process goes to step P17. Proceed to page ₁₇ .

In steps P ₁₇ and P ₁₈ , the steering rotation detection means 35
Detection signals S ₃ and S ₄ of the steering rotation speed are sequentially read. Here, detection signals _S3 and _S4 from the steering rotation detection means 35 are shown as shown in FIG. If the read detection signals S ₃ and S ₄ are normal, the step
The process advances to step _P19 , where _S3 - _S4 is calculated, and this is set _as the steering rotation speed S. This steering rotation speed S is as shown in FIG.

In step _P20 , in order to determine the direction of the steering rotation speed S, it is determined whether it is positive or negative. If S is positive, proceed to step _P21 , and at step _P21 F=0.
shall be. If S is negative, proceed to step _P22 ,
After setting F=1 in step _P22 , absolute value conversion, that is, S=-S processing is performed in step _P23 , and step _P24
Proceed to. At step _P24 , the absolute value S of the steering rotation speed is
The contents of memory with address is recalled.
In the memory, the rotation speed N _M of the electric motor 18 corresponding to the absolute value S of the steering rotation speed shown in FIG. 12 is stored.
_{In order to} determine
A table 4 is constructed in which the following are stored. Therefore, it corresponds to the address by the absolute value S of the steering rotation speed.
_D2 is called and the process proceeds to step _P25 .

In step _P25 , the direction F of the motor rotation speed control signal _D2 is determined. If F is zero, the process directly proceeds to step _P27 ; if F is 1, the process proceeds to step _P26 ; in step _P26 , the absolute value conversion is performed as _D2 = _-D2 , and the process proceeds to step _P27 . In step _P27 , the motor torque signal _D1 and the motor rotation speed control signal _D2 are added, and this is set as the motor control signal _T4 , and the process proceeds to step _P28 . In step _P28 , the sign of _T4 is determined. If T ₄ is positive, the process advances to step P ₂₉ , and in step P ₃₉ , the rotation direction control signal T ₂ =1,
Set T ₃ = 0, and if T ₄ is negative or zero, the step
After setting T ₂ = 0 and T ₃ = 1 at P ₃₀ , T ₄ at step P ₃₁
= _-T4 and proceed to step _P32 . and,
Output T ₂ and T 3 at step P ₃₂ , and output T 2 and T ₃ at step P ₃₃ .
Output T ₄ and return to step P ₁ . And T ₂
= 1, and when T ₃ = 0, the motor drive means 45
While turning on FET 47 and setting FET 49 to a driveable state, when T ₂ = 0 and T ₃ = 1,
By turning on the FET 50 and setting the FET 48 in a drivable state, the rotational direction of the electric motor 18 is controlled. At the same time, if T ₂ = 1 and T ₃ = 0 by the control signal T ₄ , the FET 49
PWM driven based on T ₄ , e.g. T ₃ = 0,
When T ₃ =1, the FET 48 is driven by PWM based on T ₄ . In addition, Figures 6, 7, and 10
α and β in the figure represent insensitive bodies, and the relationship α<β is established.

Therefore, in such an electric power steering device, as the vehicle speed increases, the auxiliary torque generated by the electric motor gradually decreases, and when driving at a predetermined high speed or higher, the auxiliary torque corresponds to the friction of the steering force booster. Torque is applied by the electric motor, and above a certain high speed, the weight of the steering feeling due to friction disappears, and a steering feeling almost equivalent to that of a manual steering device is obtained, and since the dead zone is set to α < β, the steering It is possible to eliminate the heaviness at the beginning of cutting, that is, the feeling of friction. In addition, since the configuration determines the motor control signal corresponding to the vehicle speed based on each table, instead of using conventional feedback control, the response performance of the motor is improved, and it can sufficiently respond to the operation of the steering system, providing optimal steering feel. In addition, it is easy to change the steering feel itself by changing the table.

(Effects of the Invention) As is clear from the above description, according to the present invention, the control signal for the electric motor corresponding to the vehicle speed is determined and outputted by a microcomputer instead of using conventional feedback control. The responsiveness of the control is increased, and the operation of the steering device can be sufficiently responded to, thereby providing an optimal steering feeling. In addition, since the friction of the steering force booster is taken into consideration as a control signal for the electric motor, the weight at the beginning of steering is eliminated, and the steering force booster system, which includes other elements of the steering system during high-speed driving, is It is no longer affected by friction, and it becomes possible to obtain a light steering feel that is almost the same as that of conventional manual devices.

[Brief explanation of the drawing]

Figure 1 is an overall configuration diagram of the present invention, Figures 2 to 12
The figure shows an embodiment of the electric power steering device of the present invention, and FIG. 2 shows its electromagnetic booster.
3 is a diagram showing the overall configuration of the control device, FIG. 4 is a flowchart showing an outline of the control process, and FIG. 5 is a diagram showing the relationship between steering torque and its detection signal. Figure 6 is a diagram showing the relationship between steering torque and friction control signal, Figure 7 is a diagram showing the relationship between steering torque and road load control signal, and Figure 8 is the relationship between vehicle speed and cycle. A diagram showing
Figure 9 is a diagram showing the relationship between vehicle speed and vehicle speed coefficient.
Figure 0 is a diagram showing the relationship between steering torque and electric motor torque control signal, Figure 11 is a diagram showing the relationship between steering rotation speed and steering rotation detection signal, and Figure 12 is a diagram showing the relationship between steering rotation speed and electric motor rotation speed control signal. FIG. In the drawings, 18...Electric motor, 30A...Motor control signal generating means, 30B...Road resistance control signal determining means, 30C...Friction control signal determining means, 30D, 30F...Calculating means, 31...Steering torque detection Means, 40...Vehicle speed detection means, 45...
...It is an electric motor drive means.

Claims (1)

[Claims] 1. In an electric power steering device that aims to reduce the steering force by applying torque generated by a steering force booster using an electric motor to the steering system, there is provided a steering torque detection means for detecting the steering torque of the steering system, and a means for detecting the vehicle speed. The steering torque detection means calculates the product of the vehicle speed detection means to be detected, a road surface load control signal corresponding to the road surface load based on the detection signal from the steering torque detection means, and a vehicle speed coefficient based on the detection signal from the vehicle speed detection means. a motor control signal generating means for determining and outputting a motor control signal obtained by adding a friction control signal corresponding to the friction of the steering force booster system based on a detection signal from the steering force booster system, and driving the motor based on the motor control signal. An electric power steering device comprising: an electric motor drive means.